Engineering Earthquake Structures: Day 5

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Students will be able to analyze textual evidence in order to design a structure that can survive seismic waves, and analyze multiple design choices based on criteria in order to determine the most effective design for a prototype.

Big Idea

Students dig into the differences between analog and digital signals. What's the connection to earthquakes? It's all about how waves impact our lives in the real world!

Connecting to the NGSS and the Common Core

Over the course of  4 – 5 days, students design earthquake resistant structures based on their research of seismic design principles.  Along the way, students utilize scientific text strategies, engage in scientific discourse based on evidence, experience the engineering design process and are introduced to the advantages of digital vs. analog signals.  Components of this lesson connect to the following NGSS and Common Core Standards:

MS-ETS1-1  Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

MS-ETS1-2. Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

MS-ETS1-3. Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

MS-ETS1-4. Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process

MS-PS-4-2  Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.

MS-PS-4-3  Integrate qualitative and technical information to support the claim that digitized signals are a more reliable way to encode and transmit information than analog signals.

On day one, students analyze text so that they can obtain and evaluate information (SP8) and engage in evidence based discussions (SP7). 

Day two, students use a design matrix  to determine which design solutions meet the criteria (ETS1-2) and begin testing their designs on the shake table.

On day 3, students begin to shake their initial prototypes and collect qualitative and quantitative data to create new design solutions.  In addition, they work on generating questions and engage in scientific discourse as they explore connections to wave properties as the listen to the "song" or "sound a comet makes" that was collected by the Rosetta probe that landed on Comet 67P/Churyumov-Gerasimenko!

On day four, as students test their earthquake resistant structures they improve their designs based on the results (ETS.1).  Moreover, students compare their results with other groups and designs to incorporate all successful components into a “super design” (ETS1-3).  In addition, students are introduced to the difference between an analog and digital signal.

Day five of this lesson asks students to look at real world constraints and impacts.  After developing their classroom prototype, students consider real world implications to society and the environment.  They recognize that technologies have limitations and that while prototypes meet our societal needs and wants, they also have short and long term consequences.  During this lesson, students further their understanding of analog and digital signals as the teacher takes the students through a visual model/analogy with a children's swimming pool!

Connecting to the Essential Question: What am I going to be learning today?

5 minutes

Ask students, “What are you going to learn today?”.  Students should respond by stating something connected to the NGSS Essential Question (I keep this posted on my front board.).  Thus, students might say, “We need to answer the question, what are the characteristic properties of waves and how can they be used in the world?” .

Explain that our focus over the today will continue to lie in how waves can be used in the real world.  Explain that while we will continue to look at seismic waves, we are adding a focus on how analog and digital signals differ and the advantages/disadvantages of each type of transmission.

Say, "Yesterday, we were introduced to the difference between an analog and digital signal.  On your fingers, give me an idea of your level of mastery on this concept (with 4 being mastery).  Today we will continue to build on this understanding."

Show the students the images from the previous lesson that show the differences between some analog and digital devices.

One quick place to find a few pictures of objects using analog and digital signals is at Sparkfun, created by Juan Pena.

Another picture I use comparing analog and digital television can be found at PBS.

Say, "Yesterday we also watched a video explaining the difference between analog and digital signals.   What are some of the properties of both types of signals that you remember?"

Students may offer things such as:

  • "Both signals can lose energy as they transmit."
  • "Analog signals aren't as clear as digital signals."
  • "Digital signals use 1's and 0's"
  • "Analog signals look like transverse waves while digital signals look 'rectangle-ish'"
  • "Analog signals deteriorate more than digital signals."
  • "Analog has a range of values and digital only has set values."
  • "Both are waves."
  • "Things now-a-day are mostly digital."
  • "Analog is like clocks with 'hands' where digital says the numbers."

Say, "In today's lesson, you are going to be focusing on more of these similarities and differences as well as the advantages and disadvantages of each type of signal."

Mini Lesson: Modeling Analog and Digital Signals Demonstration

20 minutes

This model provides the student with an analogy for digital and analog signals.  I created this demonstration after reading this Radio article from EXPLAINTHATSTUFF!.

For this mini lesson, you will need a kid pool filled with water, about 20 - 30 rubber ducks, and a few toy boats.  Have students fill in around the pool.

***The dialogue below is a way that the conversation and demonstration could unfold.  The video clips included do not include all of the discussion, simply some quick clips of the pool and the actual movements you might do to model this analogy.

Explain to students that one example of analog and digital signals can be shown with radios.  I show students this image and give a brief introduction to how radio waves travel from a transmitter to a receiver.  I explain that when an electronic signal travels to a transmitter, electrons move and create radio waves that then travel to a receiver.  Once the signal (radio waves) reach the receiver, it causes the electrons in the receiver to vibrate in the same way that the original electrons in the transmitter had vibrated.  These vibrations can be used to recreate the original message.

Ask the students to recall the Radio Transmission article about AM and FM signals that they read in the previous class period.  

Teacher:  "What do AM and FM mean?".  

Student: "Amplitude Modulation" and "Frequency Modulation".  

Teacher: "Amplitude Modulation", what does amplitude mean again?"

Student:  "How much energy a wave has."

Teacher:  "How do we measure the amplitude of a transverse wave?" (This was taught in a previous lesson.)

Student: "From a line through the middle of the wave to a wave or crest." or "It's like half the 'height' of the wave."

Teacher:  "What does FM mean?"

Student:  "Frequency Modulation"

Teacher:  "Frequency Modulation, what does frequency mean again?"

Student:  "It is like the speed of a wave." or "It's how many waves are passing a point in a particular period of time."

Teacher:  "Awesome.  I want to show you an analogy using my kid pool to help you picture this more clearly.  Pretend that I am the radio transmitter and am on this boat in the middle of the 'ocean' and you are the radio receiver and are on the 'shore'.  Let's say that there are some waves around my boat.  And, let's say that I wanted to send you a signal that my boat has run out of gas in the form of water waves. Before I went out in the ocean, I let you know what the waves I would send would look like if I was in trouble.  Let's watch what happens to my waves as I send them to shore."

Teacher:  What do you notice happens to the waves as they move towards the shore?

Students may respond with, "the waves get slower" or "the waves get shorter".  Even better, students say, "the waves decrease their amplitude and increase the wavelength as they head towards shore."

Teacher:  I notice that the waves are changing as they head to shore. What could I do to ensure the waves, my "message", gets to shore?

Students often say, "rock the boat harder" or "give your waves more energy".

Teacher:  Yes!  In order to get these waves to you, I could rock my boat up and down harder (actually rock the boat in the kid pool up and down), changing the height of the wave as it moves towards the shore.  In this case, I would be transmitting my message through amplitude modulation, or an AM signal.  I am changing the amplitude of the wave to get my message to you.

Teacher:  Is there anything else I could do to get my message to shore?

Students may say "make the waves go faster" or "increase the frequency".

Teacher:  I see, I could take my hand and push the waves to you faster (Take your hand and push waves from the boat towards the students.).  In this case I would be transmitting my message through frequency modulation, or an FM signal.  I am changing the frequency of the wave to get my message to you."

Teacher:  "In an analog signal, the shape of the wave is manipulated in order to send the message from the transmitter to the receiver.  The problem with analog signals is that other things can disrupt or affect the wave.  For example, pretend another boat zoomed by towards the shore while I was sending my wave signal (Make waves from the original boat and have a student take another boat can push it through the waves you are making.).  What do you notice happens to my message?"

Student:  "Your waves look different."  or "The boat made it's own waves." or "The boat messed up your message."

Teacher:  "Absolutely!  If you were trying to listen to this message on the radio, the sound could be 'crackly' because the message got disrupted.  Digital radio can help fix this problem because the message is in a number format so it doesn't get affected in the same way."

Teacher (Referencing the Radio article mentioned earlier):  "For example, instead of sending my message in the form of waves that can get disrupted.  I could send you a number message on rubber ducks that would be carried by the waves to shore.  Now, if I get into trouble, and want to send a signal to shore, I could send you an emergency message "12345"." (actually show the students this by releasing plastic ducks to the "shore").

"To improve the signal further, if I have a problem I might send ducks with the numbers 1, 2, 3, 4, and 5 - but instead of sending just five numbered ducks, I can send ten of each duck to increase the chances of the message arriving (Actually send more ducks of each number so the students can see it, make sure to only send them in a narrow width, like the length of the boat.  This will be important later.). Now, even if the sea is choppy or a speedboat cuts through, there's still a good chance enough of the ducks will get through to complete the message.  Eventually, waves will carry ducks with the numbers 1, 2, 3, 4, and 5 to shore (Ask the student that moved the second boat through again to disrupt the ducks.  I even have more students move boats through.).   Even with the extra boats, you still can put the 1, 2, 3, 4, 5, ducks together and figure out what I'm trying to say."

Teacher:  "Another example of an advantage of digital radio signals is that they travel on a wider "band width" than analog signals.   They can cover a wider area than analog signals.  In our boat example, if I send a signal that covered a much wider area, let's what the benefits would be.  Will the signal avoid speedboats and get to the shore more easily? Let's see!" (Send the ducks out of the boat in a wider band and send the extra boats through again.)

For even more detail, I encourage you to read the Radio Article from EXPLAINTHATSTUFF!

Seismic Design Principles: Engineering Earthquake Structures

25 minutes

Explain to the students that engineers in the real world have constraints that are present in every task or problem they solve.  Explain that in the classroom, we also constraints that may deal with materials and time. But when we replicate (or try to) real world engineering challenges, with them comes real world constraints.  As a class, brainstorm a list of these constraints and have students add them to their lab sheet.  For my class, at this point in the year we have discussed this idea so the conversation goes pretty quickly.  Students should offer suggestions such as "economic factors", "safety factors", "health effects", and "environmental consequences".

Let students know that today is the closing day for their earthquake structures.  Students should not begin a new design on this day.  This time is really set aside for any group close to shaking their last structure the day before but did not have time.  Once groups have completed their last shake, they should put away their materials and begin on a reflection of their group's engineering design process.   Each individual student should write their own written reflection.  Ask the students to include these responses in their reflection:

What did your group do well that aided in the design process?

What improvements would you like to see your group make if you were to go through this process again?  (I am not talking about improvements to the actual design of the structure. I am asking the students to focus on the improvements the group should make in their process of solving this problem.)

From your experience, what are the most important elements of the design process?

For me, students that do not finish their reflections in class complete it as homework.

Below are some reflections students tend to make:

This student reflects on the importance in listening to all group members options and how not doing this can result in "first attempts in learning."  (In my class, we talk about epic f.a.i.l.s. or epic first attempts in learning and how failures are to be celebrated because we can learn from them.)  The student also identified that the most important part of the process was researching.  I find this a big growth statement for middle schoolers.  Many students want to rush into design and engineering work and just get to the building.  This student recognizes that researching may actually be the most important part.

The student below mentions that after their first model failed they "didn't come up with another plan and just built as they went along."  He also mentions that the most important part of the design process was the "design matrix and creating a plan."

The student below explains that the most important part of the design process was making multiple designs (NGSS - Optimize!) and to research again before each design.

This student recognizes the importance of not just "taking the design apart".  Groups should discuss the flaws and areas of strength in their designs prior to disassembling. 

Closure: Shape Vocabulary

20 minutes

With about 20 minutes left in the class period, have students clean up their earthquake materials and return to their seats.

Provide each table with a white board and a dry erase marker.  If you do not have small white boards white paper and markers would work as well.  Explain to students that they are going to do a representation of the words analog signal and digital signal.  Ask each table to work together to write each of those in the shape of its definition.  Tell the students that they can add small pictures, but the way that the word is written should be in a shape that shows meaning.  For example, during the our previous energy unit, students drew a circle with the word radiation as all of the light rays coming off the circle to make it look like a sun. (For another example of writing vocabulary words in the shape of their definition, see this lesson.)

After each group is finished, have them present to the class their drawing and explain how the picture shows the meaning.  


Students that presented the above shape vocabulary to represent analog signals.  As these groups described their representations they noted that the amplitude and wavelength of the wave varied and that the wave picked up noise as it moved along.  In addition, they noted it was important that analog signals vary over time so they drew a smooth curve for their wave.

Students that presented the above shape vocabulary emphasized that their designs were showing that digital signals take "readings" at discrete points and so the signal is not fluid like an analog wave.  The student on the right used the path of one cell phone, to a tower, to a satellite, and back to another cell phone to show the path of a digital signal.

The student above took a different approach.  They showed a digital device sending out many of the same signals (one of the advantages of digital signals they learning about in the duck and kiddie pool demonstration).